This application relates to the inclusion of a restriction in a line leading to a compressor in a refrigerant system to allow easy capacity correction for the refrigerant system.
Refrigerant systems are utilized in many air conditioning and heat pump applications for cooling and/or heating the air entering an environment. The cooling or heating load on the refrigerant system may vary with ambient conditions, and as the temperature and/or humidity levels demanded by an occupant of the environment change.
One goal in the design and application of refrigerant systems is a need to closely match a compressor displacement (its capacity) to the system requirements. As known, compressor models are available in stepped increments in size (displacement). Often, the required compressor displacement for a particular application falls “in-between” the available sizes, however. This can result in a system being oversized for a particular application, since the next available compressor of a larger size is typically selected. Having an oversized system is undesirable as it reduces system efficiency, since the heat exchangers now become undersized for the selected compressor, resulting in lower than desired saturation suction and higher than desired saturation discharge temperatures. Further, system reliability as well as temperature and humidity control may be compromised, since the system may cycle on/off more often than desired.
Additionally, lower than normal suction and higher than normal discharge pressures may cause nuisance system shutdowns if diagnostic controls see what would appear to be a problem.
One way refrigerant system designers have addressed these concerns is to provide an electronic suction modulation valve between the evaporator and the compressor. While this does allow modulation of the amount of refrigerant delivered by the compressor, a suction modulation valve presents a relatively large expense. Further, additional controls are required, and such valves are difficult to retrofit into existing refrigerant systems without further redesign. Also, as the refrigerant flow is reduced by an electronic expansion valve, the refrigerant superheat entering the compressor is typically increased as well. This results in higher discharge temperatures and may result in oil logging in the suction line, which is undesirable.
Therefore, there is a need for a simple and effective solution to reduce compressor displacement in order to match it to a particular system and to satisfy application requirements.